technological requisites for induction heating with rotating ......2019/04/05 · induction heater...

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Technological requisites for induction heating with rotating magnetsAluminium extrusion congress 4th April 2019

Speakers:Prof. Fabrizio DughieroIng. Marcello Zerbetto

Introduction

University of Padua

• Padua is a city in the north-east of Italy, 30km from Venice (250.000 people – 50.000 students).

• The University foundation year is 1222 (Galileo Galilei was teaching in Padua)

• Now the 797th Academic Year is running!

• 11,000 students are enrolled in the Engineering undergraduate and Graduate courses

• The Department of Industrial Engineering hosts The Laboratory for Electroheat of Padua (LEP)

04/04/2019 Aluminium extrusions3

Laboratory for Electroheat


▪ The Laboratory for Electroheat (LEP) of Padova University has been established in 1969 by prof. Ciro Di Pieri, emeritus professor, and developed by Prof. Lupi, emeritus too, who has been retired since 2010.

▪ The research activity of the Laboratory has always been devoted to the industrial applications of electroheat technologies and, in particular, to direct and indirect resistance heating, medium- and high-frequency induction heating and dielectric/microwave heating.

▪ A close cooperation exists among Laboratory, manufacturers and end users of electroheat equipments and processes, in the frame of research contracts on specific topics.

▪ LEP has also a lot of international agreements with universities and research centers all over the world

Inovalab


• InovaLab is a spin-off company ofPadova University, founded in 2004 bytwo researchers of the Department ofElectrical Engineering, with a longexperience in the field of Electroheatapplications.

• The mission of InovaLab includetechnology transfer to industry and thedevelopment of innovative processesand prototypes by using modernsimulation software, specificlaboratory testing, and takingadvantage of high level team skills.

• InovaLab is the R&D center for many companies; co-operation is the main word used in InovaLab. The customer is a partner and InovaLab is not only a supplier but a real R&D center outside/inside the customer facilities, with skills, tools, instrumentation and personnel which can be involved in the projects.

Inovalab and Lep facilities and instrumentation


• Several multicore workstations with up to 400 GB RAM and 32 cores processors

• Simulation softwareAltair suite:

• FLUX 2D-3D

• FEKO

• ACU Solve

▪ COMSOL multiphysics

▪ Labview

▪ Matlab

Aluminium billet heater

Aluminium billet preheating contest

In the extrusion industrial plant aluminium billets are preheated at about 400-500 °Cbefore being pushed through a shape die. Frequently to have an isothermal extrusionprocess a conical temperature distribution along the billet axis (named “taper”) isrequired.

Today the main heating technologies used for aluminium are:

▪ Gas furnaces with low thermal efficiency of 40-45%, high CO2 emission but with costcompetitiveness (low gas cost)

▪ Traditional induction technology where the magnetic field is generated by watercooled multi turn coils; with efficiency of 55% because the aluminium is non-magnetic and high conductive material.

▪ An improvement of induction technology is proposed by some authors in which thebillet is forced to rotate inside a transverse DC magnetic field produced bysuperconductive coils. This approach has high efficiency about 85% but requirescomplex and expensive setup (cryogenic system, superconductive magnets, veryrobust rotating system with large braking torque) and the application in industrialcase is very difficult.


Concept of Aluminum billet heater proposed by InovaLab

The technology proposed by InovaLab in collaboration with the University of Paduaconsists to clamp an aluminum billet inside a rotating system of permanent magnets.This solution (patented by InovaLab) with respect to the traditional technologies (Gasand Induction heater) allows:

▪ The achievement of high efficiency about 30% higher respect to the traditionalinduction heater without using water cooling

▪ a best temperature profile along the billet axis (taper) splitting the rotor machine inseveral modules which rotate at different speeds in opposite direction to reduce thebraking electromagnetic torque on Al billet.

The first industrial scale prototype for 200 mm diameter, 500 mm length aluminumbillet with rated power of 55 kW has been realized in 2011 at University of Padua.


Magnheat project

Magnheat & Life + program

The LIFE programme is the EU’s funding instrument forthe environment and climate action. The generalobjective of LIFE is to contribute to the implementation,updating and development of EU environmental andclimate policy and legislation by co-financing projectswith European added value.In particular Magnheat project was a LIFE+Environment Policy & Governance program.

It co-financed innovative or pilot projects contributing tothe implementation of European environmental policyand the development of innovative policy ideas,technologies, methods and instruments.


Magnheat project

MagnHeat project aims to demonstrate the first full scale industrialapplication of a novel concept of DC induction heating furnace, which hasnever been applied so far, based on rotating permanent magnets forAluminium extrusion. Such technology has been developed through acombination of eco-design and engineering, exploiting and valorizing R&Dactivities carried out by the coordinating beneficiary (INOVALAB).

Technical performance, environmental and economical benefits of MagnHeatinduction prototype has been proven in a concrete large scale industrialproduction line (PANDOLFO). Established methodology for environmentalimpact and thermo economic assessment have been used to gatherquantitative results (CIRCE). The national association of Aluminium industries(ASSOMET) has been involved to gather the attention of all relevantstakeholders and ensure proper dissemination and promotion of the actionthrough the EU.


Magnheat Technology description

The concept of the technology is the rotation of permanent magnets around the billet. The design of the heater has been done by mean electromagnetic and thermal FEM simulation.


Specification of the first industrial prototype.


Sizing of single module: FEM 2D analysis


➢ The electromagnetic sizing of rotor module of permanent magnet heater has been carried out using FLUX2D model with transient magnetic application coupled with Got-it tool for optimizing the use of magnets and the performance.

Billet

Back iron

Magnet

Tube Aluminum

Thermal insulatorMagnet separators

2D transient magnetic model.


The model simulated is relative of only one magnetic pole

The input variable used in the optimization are:▪ Magnet thickness Hm▪ Number of magnetic pole Np▪ Rotation speed RPM

The output metrics are:▪ The weight of permanent magnets Wmag▪ The power transferred in the Al billet PAl▪ The electromagnetic braking torque Cem

Optimization result


The problem is multi objective with the following goal functions that are minimized:▪ OF1=Wmag/PAl▪ OF2=PAl-Ptarget

Note: the optimisation is done with the 2D FEM model to reduce thecomputation time, one solution 2D takes about 3 min. and one solution 3Dtakes about 2 h and 20 min; but the model 2D is approximated because itdon’t take into account the real distribution of flux density along the axisdirection on the billet surface. This distribution is reproduced correctly only inthe 3D model. The difference between 2D and 3D model is about 20% for thegeometric configuration chosen, so to obtain by the optimisation tool acorrect result the power target will be increased of 20%.

3D transient magnetic model.


The model simulated is relative of only one magnetic pole

Geometry put on 3D model Mesh used on 3D model

Back iron

Al billet

Magnet separators

Comparison between 2D and 3D FEM model


Comparison of flux density distribution in the radial direction in a transversal section

Flux density distribution in the axial direction for the 3D model

Electromechanical performance of optimized module


➢ The optimized module has the following performance in function of rotational speed (2D-3D model). ▪ T electromagnetic braking torque▪ P power transferred in the Aluminum billet

3D transient thermal model


▪ A 3D simplified transient thermal model is solved to predict the temperaturedistribution in the billet. Since the process involves a small temperature variation (about 100 °C from 400 to 500 °C) the variation of resistivity is neglected and it is considered constant at an average value.

▪ The induced power density has a radial and azimuthal distribution (a) that rotates following the magnetic rotation. However the power density put in the thermal model (b) is an average value in an electric period of real instantaneous distribution. The average value is calculated for each nodes using a python script.

(a) (b)

Thermal transient result


Thermal transient as function of time. The curves describe the temperature on the surface Te and axis Ti evaluated on the top and bottom part of billet.

Heater realization

technological requisites for induction heating with rotating ......2019/04/05 · induction heater...

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